The present invention relates broadly to a sealing gasket for use within the exhaust system or the like of an internal combustion engine, and particularly to a gasket construction including one or more lamellar graphite seal members received within apertures formed in a metal retainer member.
Sealing gaskets of the type herein involved are employed in internal combustion engines as interposed for compression between certain mating surfaces of the engine for effecting the fluid-tight sealing thereof. For example, within the exhaust system of the engine, gaskets of such type are used to seal the interfaces between the connecting flanges of exhaust pipes, or between a header flange or other exhaust manifold and the cylinder head. In basic construction, these gaskets are conventionally formed as a generally planar member consisting of one or more layers of fiberboard, graphite, and/or a metallic material such as copper, steel, aluminum, or the like. Within the planar member are formed a plurality of apertures for registration with the fluid passageways of the exhaust pipes or cylinder head and manifold. Bolts or other fastening members typically are employed to develop compressive forces within the interface for securing the assembly into a fluid-tight joint.
A representative gasket for use in a flange-type pipe coupling is disclosed in Glasgow, U.S. Pat. No. 3,302,953. The gasket includes an outer metal ring portion having a plurality of peripherally-spaced bolt hole apertures and a central fluid passageway. A pair of diverging, annular sealing lip portions are provided to extend inwardly from the innermost edge of the outer ring portion to form an inwardly-facing annular groove. A resilient sealing ring formed of a synthetic rubber material or the like is molded within the groove to provide a low pressure seal. As interposed between a pair of pipe flanges, the sealing lip portions of the outer ring are compressed to provide a high pressure seal and to prevent the extrusion of the resilient sealing ring.
Meyers, U.S. Pat. No. 3,841,289, discloses a composite cylinder head gasket for an internal combustion engine which includes a metal sheet. On either side of the metal sheet is coated a layer of a sealant. The sealant is preferably formed of a laminated graphite sheet or foil having a density which is substantially less than its fully compressed density. Upon the installation of the gasket between opposing surfaces of the cylinder head and block of the engine, the tightening of the head bolts to a desired torque compresses the gasket such that portions of the graphite material are compressed to a maximum density.
Dinger, U.S. Pat. No. 3,942,807, discloses a sealing arrangement between a cylinder crankcase and a cylinder head. A seal for the arrangement is constructed as having an outer flat metal portion to which is bonded an inner elastic seal ring or liner of a vulcanized rubber or the like.
Sugawara, U.S. Pat. No. 4,243,231, discloses a cylinder head gasket which includes a base sheet having a plurality of holes with a cut-out area adjoining the holes. Within the cut-out area is mounted a graphite sheet which is described to resist deterioration within the narrow area between the adjoining holes.
Kanczarek, U.S. Pat. No. 4,690,438, discloses a gasket construction including an incompressible base portion formed of a pair of concentric rings having a slot therebetween. Within the slot is disposed a soft-material insert formed of expanded graphite.
Kawata et al., U.S. Pat. No. 4,756,561, discloses a gasket for use between connecting flanges in exhaust system of an engine. The gasket is constructed of a pair of thin metal sheets between which is interposed an intermediate layer formed of a blend of ceramic fibers and a thermally-expandable filler material such mica or vermiculite particles. A gas passage aperture is formed through the center of the gasket, with bolt holes being formed on opposite sides thereof. An annular metal insert member optionally may be provided about the bolt holes to support the bolt tightening forces such that the bolts may be torqued without developing excessive pressure on the intermediate layer. In operation within the engine, the heat transported with the exhaust gas effects a thickness expansion of the intermediate layer, which expansion is relieved as the intermediate layer contracts upon cooling.
Dennys, U.S. Pat. No. 5,222,744, discloses a sealing gasket for a flanged pipe coupling which includes a packing of expanded graphite disposed between an inner and outer metal reinforcement rings. The two rings are oriented on different planes prior to clamping between the pipe flanges, with the graphite packing being made to be applied against the bearing surfaces of the flanges. As the flanges are clamped, opposing forces are developed which effect the compression of the packing.
Latty, U.S. Pat. No. 5,413,359, discloses a gasket which includes an inner annular metal core, and an outer compressible ring of an expanded graphite material. The metal core has a circular recess on an outer circumference thereof which is provided in the form of a V-shaped trough. The gasket ring is inserted in the recess in alignment with the core.
Borneby, U.S. Pat. No. 5,531,454, discloses a laminated cylinder head gasket. The laminate is formed of an inner layer of a metal plate interposed between outer layers of an expandable graphite material. The graphite material is a mixture of expanded and unexpanded graphite which, upon heating, expands to create an outward pressure that is stated to improve the sealing ability of the gasket.
Header and header collector or exhaust pipe flange gaskets are marketed commercially by Mr. Gasket of Cleveland, Ohio. Such gaskets include a single-layer construction of a fiberboard material, and a laminated construction having a metal core. Gaskets of such type, which may additionally include a non-stick coating are also manufactured by Fel-Pro of Skokie, Ill.
The above-described references heretofore have constituted the state of the art with respect to cylinder head and collector gaskets. With respect to gaskets conventionally constructed of a fibrous or other relatively soft material, it will be appreciated, however, that the total compressive forces developed within the interface must be supported by such material. Over time and under repeated thermal cyclings, certain of these materials may have a tendency to develop a compression set which, in turn, may result in a loss of torque within the fastening members and a loosening of the joint. Moreover, as no positive means typically is provided in such gaskets to delimit or otherwise control the compression of the gasket, the gaskets may be over-compressed during installation or maintenance which again leads to the development of a compression set within the gasket.
In view of the foregoing, it is apparent that continued improvements in such gaskets would be well-received by the automotive industry for use as original and replacement equipment in passenger cars, and by enthusiasts for use in racing and other high performance applications. A preferred gasket construction would be economical to manufacture, but would exhibit excellent sealing with a minimum of compression set and resultant torque loss. Such a gasket additionally would be capable of withstanding prolonged exposure to high temperatures as well as to hydrocarbons and other fluids within the rigorous service environment of an internal combustion engine.